1. Field of the Invention
The present invention relates to a power supply control apparatus and a power supply control method for use in an electronic device that runs a particular process when the power supply of the electronic device turns off.
2. Description of Related Art
Electronic devices that run a particular process when the power supply unit of the electronic device turns on or turns off are taught, for example, in Japanese Unexamined Patent Application H09-11452 (see page 7 and FIG. 6) and in Japanese Unexamined Patent Application 2000-168096 (see pages 9–10 and FIG. 11 and FIG. 12).
Japanese Unexamined Patent Application H09-11452 teaches an inkjet printer with a function for appropriately controlling the temperature of the print head. More particularly, this inkjet printer maintains the supply of power to the printer control circuit when the power supply unit turns off, calculates the time required for the print head temperature to stabilize after the power turns off based on such factors as the ambient temperature, manages the temperature of the print head while waiting for the calculated time to pass, and turns off the supply of power to the printer control circuit when the calculated time has elapsed. If the printer power turns on again before the calculated time passes, however, the printer control circuit controls the temperature of the print head to a temperature suitable for ink discharge based on the temperature of the print head when the power supply was turned on again.
Japanese Unexamined Patent Application 2000-168096 teaches an inkjet printer having a function for running a print head cleaning process. More particularly, this inkjet printer stores the status of the cleaning process if the power supply turns off due, for example, to a power outage while cleaning the print head. When the power is restored and the power supply is turned on again, the printer checks a flag denoting whether a cleaning process was interrupted, and runs an initialization process determined by the type of cleaning process that was interrupted if a cleaning process was in progress when the power supply was cut off. For example, a wiping initialization process runs if a wiping process was running just before the power failed, a vacuuming initialization process runs if a nozzle vacuuming process was interrupted, and a rubbing process runs if a rubbing process was interrupted by the power outage.
The purpose of these conventional power supply control methods is to maintain the power supply for a specified period of time after the power supply turns off in order to save data required to resume the operating status of the device before the power supply shut down, or to calculate the time until the temperature of the print head stabilizes. The purpose of these conventional power supply control methods is not to lower the frequency of specific processes when the power supply turns on so that the electronic device (printer) can be used more quickly.
If an electronic device always runs a particular process when the power supply turns on, that process still runs even if the power supply turns on shortly after the power supply turned off, and it is therefore difficult to reduce the frequency of this particular process and thereby enable the electronic device to be used more quickly after the power supply turns on. However, by monitoring whether the power supply turns on again during the period in which the power supply is maintained after the power supply is turned off, a particular process that runs when the electronic device turns on can be omitted if the power supply turns on again during this period when the power supply is maintained after the power supply is turned off.
This conventional power supply control method does not, however, monitor if the power supply is turned on again during the period in which power continues to be supplied.
Some inkjet printers, for example, have a function for cleaning the print head when the power turns on, and such printers always run the cleaning process when the power turns on regardless of whether the power turns on shortly after the power turned off. Furthermore, because the cleaning process of an inkjet printer vacuums and disposes of ink from the print head, and thus consumes ink, turning the power off and on within a short period of time consumes a large amount of ink.
Needless cleaning processes can thus be eliminated by preventing the power supply from turning off even if the power switch is turned off, monitoring if the power is turned on again while the power supply is thus maintained, and not running the cleaning process if the power supply is turned on again during this time. Such a power supply control method is not limited to application in inkjet printers, however, and can be used in any electronic device that runs a particular process when the power supply turns on to similarly reduce the frequency of running said process. Electronic devices that must run a particular process when the power supply turns on shall not, however, be so limited.
Once an electronic device that shuts off the power supply when a specified period of time has passed after the power supply is turned off enters the process for terminating the power supply, the electronic device will not restart the system even if the power supply switch is turned on again before the power supply voltage drops to the reset voltage, and the system remains off even though the power supply switch is in the on position. This is particularly unintuitive and not user friendly when the on/off status of the power supply switch is visually apparent, such as when the power supply switch is a seesaw switch or a push-button switch that is pushed down to a depressed position when on and is pushed again and released to a raised position when off.
Although a mismatch between the position of the power supply switch and the on/off operating status of the system does not occur when the on/off position of the power supply switch is not visually apparent, some other means of informing the user whether the power supply is on or off must be provided, and this increases the cost accordingly.
The present invention is therefore directed to solving the foregoing problems. The power supply control apparatus and power supply control method of the present invention maintains the supply of power in an electronic device for an extended time period after the power supply switch is turned off while monitoring whether the power supply switch has been turned on again during such time period thereby eliminating the frequency of running unnecessary programs that are usually initiated each time the power supply turns on independent of how long a time has expired from the previous shut down of the power supply and assures that the operating (power supply) status of the system matches the position of the power supply switch.